One-in-five buildings have been in the earthquake-stricken zone have collapsed, with 60 per cent showing cracks, Gansu Television reported.

"More than 21,000 buildings were severely damaged and more than 1,200 have collapsed,'' a local government official at the provincial earthquake bureau in Dingxi told AFP, adding that 371 aftershocks had been recorded.

Eight towns in remote, mountainous areas have been seriously damaged in the earthquake and subsequent flooding and mudslides, Xinhua News Agency reported.

Power outages and communications were cut off in 13 towns in Zhangxian county, Xinhua said.

The Lanzhou military region has dispatched 1000 soldiers with Gansu Military police sending 500 troops to assist in rescue efforts, Phoenix News reported.

Rescuers are battling to reach survivors in remote areas.

The quake hit near the city of Dingxi in Gansu province, a region of mountains, desert and pastureland with a population of 26 million. It is one of China's more lightly populated provinces, although the Dingxi area has a greater concentration of farms and towns with a total population of about 2.7 million.

Pictures broadcast on state television showed rural villages with rubble-strewed streets and houses crumbled. Locals in Minxian county in Gansu province, said they saw trees and homes shaking, with the quake lasting for about one minute.

Earlier, an official surnamed He from Minxian, said there were 19 dead and more than 200 injured in seven townships severely hit by the quakes. The Chinese government measured the first earthquake at 6.6 magnitude

The quake hit near the city of Dingxi in Gansu province, a region of mountains, desert and pastureland with a population of 26 million. That makes it one of China's more lightly populated provinces, although the Dingxi area has a greater concentration of farms and towns with a total population of about 2.7 million.

Deaths were also reported in Min County in the rural southern part of Dingxi municipality, the Xinhua News Agency reported.

Residents described shaking windows and swinging lights but little major damage and little panic. Shaking was felt in the provincial capital of Lanzhou 177 kilometres north, and as far away as Xi'an, 400 kilometres to the east.

"You could see the chandeliers wobble and the windows vibrating and making noise, but there aren't any cracks in the walls. Shop assistants all poured out onto the streets when the shaking began,'' said a front desk clerk at the Wuyang Hotel in the Zhang County seat about 40 kilometres from the epicentre. The clerk surnamed Bao refrained from identifying herself further, as is common among ordinary Chinese.

The government's earthquake monitoring centre said the initial quake at 7:45am (8.45am AEST) was magnitude-6.6 and subsequent tremors included a magnitude-5.6.

The quake was shallow, which can be more destructive. The centre said it struck about 20 kilometres beneath the surface, while the Gansu provincial earthquake administration said it was just 6 kilometres deep.

Much of western China is prone to earthquakes.

A magnitude 6.6 earthquake in neighbouring Sichuan province killed about 200 people earlier this year, five years after almost 90,000 people were killed in a huge tremor in the same province.

China's worst earthquake in recent years was a 7.9-magnitude temblor that struck the south-western province of Sichuan in 2008, leaving 90,000 people dead or missing.

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